The invention relates generally to colored lenses and more particularly to a method for color matching and dyeing lenses by converting color information into numerical values and using those numerical values to formulate a dyeing prescription.
Lenses are commonly colored by mixing additives, such as dispersable dyes and dyeing auxiliaries with water to yield a colored dye bath, heating the colored bath to about 70.degree.-90.degree. C. and dipping the lens into the dye bath. The density or intensity (concentration) of the lens coloring is determined by the length of time the lens is immersed in the dye bath and the temperature of the bath. When a dye bath is compounded with several types of dyes, the hue may also start to change with increased dipping time. Accordingly, selecting a particular dye bath and the toning that is necessary in order to obtain a desired color, as well as determining the dipping time and the work for color assessment and shading of the colored lens is highly labor intensive. It depends largely on the ability of skilled workers to make these determinations and is not well suited to mass production techniques. These drawbacks lead to increased costs and decreased quality control.
It typically takes at least about 2 years for an individual to develop the requisite skill to formulate a suitable dyeing prescription, including selecting the dye bath, dyeing times and compounding dyes and to make a proper judgment regarding the dyed color. Presently, the number of skilled workers is limited and this reduces the availability of dyed lenses as well as increasing the cost thereof. Furthermore, it is difficult for even skilled workers to obtain the desired color on the first try and this leads to repetitive dyeing operations for shading. This lowers productivity. In addition, different individuals attempting to match the same color will frequently prepare lenses having slight differences in color.
To reduce the number of man hours necessary for the lens dyeing procedure, lens dyers typically prepare a large number of standard dye baths. Each bath is for a particular color and standard dipping times are determined for each standard color bath. However, if a lens dyer is to have a large number of standard colors, as many standard dye baths are required. For example, more than 200 dye baths have to be available for the more than 200 standard SEIKO Colors available from the SEIKO Company. This large number of dye baths occupy excessive space in the lens dyeing facilities.
To dye lenses, an operator inspects a sample color and selects either an existing dye bath for a similar color from among those already prepared or prepares a fresh dye bath by mixing the appropriate dyes. The operator must then judge the appropriate dipping time in order to insure proper color density.
Computer color matching (C.C.M.) is becoming popular in other fields. A computer is used at a dyeing site for color matching dyes to selected colors. However, C.C.M. techniques have not yet been established for the dying and color matching of lenses, such as for eye glasses. Accordingly, C.C.M. is not available for the dyeing of lenses.
Conventional eye glass dyeing methods have additional drawbacks. Orders for colored eyeglass lenses are commonly received in one of two ways. In one case, a customer chooses from among standard colors of a colored lens maker. In a second situation, the selector chooses a nonstandard color and requests the lens dyer to match the selected color. Excessive delay is present between the time when the order is placed and when the final product is ultimately delivered. Transportation costs are involved and the responsibility for storing and caring for the lenses is spread among many individuals, rather than remaining at the point of sale.
Accordingly, it is desirable to overcome the drawbacks of conventional dyeing and color matching methods and to provide a dyeing and color matching method for lenses by which a suitable dyeing prescription can be prepared promptly by means of precise color matching so that a highly skilled operator is not required to engage in dyeing operations and to improve productivity and color quality of dyed lenses.